//zadacha4
bool isProgression(stack<double> myStack)
{
double first;
double next;
double difference;
if (myStack.length() <= 2)
{
return true;
}
myStack.pop(first);
myStack.top(next);
difference = first - next;
while (myStack.length() >= 1)
{
if (difference != first - next)
{
return false;
}
myStack.pop(first);
myStack.top(next);
}
return true;
}
